Microlithography finds application in the production of micro-structured components such as for example integrated circuits or LCDs. The microlithography process is carried out in a so-called projection-exposure apparatus which includes an illumination system and a projection objective. The image of a mask (also referred to as reticle) which is illuminated by means of the illumination system is projected by means of the projection objective onto a substrate (e.g., a silicon wafer) that is coated with a light-sensitive coating (referred to as photoresist) and is arranged in the image plane of the projection objective, the purpose of this projection being to transfer the mask structure onto the light-sensitive coating of the substrate. The contrast of the mask's image on the light-sensitive coating can affect the fidelity of transfer of the mask structure to coating.